"num" parameter and expected output buffer size in EVP_CipherUpdate

Tomas Mraz tomas at openssl.org
Fri Dec 16 14:26:28 UTC 2022

On Fri, 2022-12-16 at 12:08 +0100, Wiktor Kwapisiewicz wrote:
> Hi Tomáš,
> On 16.12.2022 11:53, Tomas Mraz wrote:
> > Of course once you feed the data to EncryptUpdate by chunks sized
> > smaller than block size, there logically has to be some caching
> > involved as a block cipher must encrypt only full blocks unless
> > there
> > is some padding involved but that applies only to the last block.
> Okay, if I understood you correctly there's no API to ask an already 
> intitialized EVP_CIPHER_CTX object about the cache as this is 
> implementation detail?
> (I thought EVP_CIPHER_CTX_get_num would do that but apparently
> not...)

Yep, there is no such API. Especially the provider interface does not
provide any such call.

Tomáš Mráz, OpenSSL

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